Saturday, October 29, 2011

The Elwha River, which runs through the heart of Olympic National Park in Washington State, is getting a makeover. Last month, the National Parks Service began removing the Upper Elwha Dam and the Glines Canyon Dam from the river. Both lack passageways for migrating salmon.

The five species of Pacific salmon which live in the Elwha River.

The Elwha River provides habitat for five species of Pacific salmon: chinook, chum, coho, pink and sockeye. By removing the two dams it will open up more than 110 km of river and tributary habitat for these fish. Currently only about 3,000 salmon return each year to spawn in the eight kilometers of habitat below the dams. Ecologists predict that number could rise to 400,000 once the dams have been removed and the ecosystem fully restored.Salmon are classified as diadromous, meaning they migrate between salt and fresh water. More specifically, they are anadromous, meaning that they spend most of their lives at sea and migrate to fresh water to spawn. Cutthroat trout, which also inhabits the Elwha, are anadromous too. The other type of diadromous fish are called catadromous. They spend most of their lives in fresh water and migrate to the sea to spawn. Most eels are catadromous.

The 182 million dollar project was funded by the Elwha River Ecosystem and Fisheries Restoration Act of 1992—the largest dam removal project in U.S. history. Since 1999, a total of 145 dams have been removed in the U.S., but none have been anywhere near the size of the Elwha dams which have trapped 14 million cubic meters of sediment since the first dam was completed in 1913. That’s enough sediment to fill 13 Empire State Buildings with some left over. The dams will have to be dismantled in stages to mitigate the effects of sediment removal on wildlife. It is expected that the restoration project will take another three years to complete. After the dams are removed, the area that lies under the lake will be revegitated to secure its banks from erosion.Tearing down the dams is the culmination of eight years of preparation, including the design of a new fish hatchery for the Lower Elwha Klallam tribe that lives there. The hatchery will release fish into the Elwha to help repopulate it. The tribe has a special connection to the Elwha because historically the river provided them with everything they needed to live. For centuries, their culture revolved around salmon which was the most important part of their diet. They have great respect for the salmon which they celebrated through ceremonies and rituals.

The Elwha dam removal and restoration project provides a unique research opportunity. The watershed offers scientists ideal study conditions since most of the watershed lies within the protected boundaries of Olympic National Park. If successful, restoration efforts in the Elwha River watershed may become a template for other watersheds in less-than-ideal conditions.

Sunday, October 23, 2011

The first electromagnet, invented in by William Sturgeon.
It was made of 18 turns of copper wire on a U-shaped iron
core. When the wires were connected to a copper-zinc-acid
battery, the electromagnet could hold 4 kg. The cups
contained mercury as an early method of making an
electrical contact between wires. The one on the left acted
as a power switch.

Hans Christian Ørsted was a Danish scientist and philosopher that discovered the unique relationship between electric currents and magnetic fields. Ørsted had been investigating electric and magnetic properties for several years, and in 1820, while preparing for an experiment during a lecture at the University of Copenhagen, he noticed a compass needle, which happened to be lying next to a wire circuit, moved when he switched the electric current on and off. He had found evidence of a direct connection between electricity and magnetism. A few months later after more intensive investigations, he published his discovery that an electric current produces a magnetic field as it flows through a wire. Soon after, there was a tremendous outbreak of research in this new field of electromagnetism, and in 1824 the British scientist William Sturgeon invented the electromagnet. Today, electromagnets are used in a variety of ways, from electric motors, transformers and generator to electromagnetic suspension for MAGLEV trains. One of the early uses for this new technology was in stage magic. The French master magician Jean Eugène Robert-Houdin used a powerful electromagnet in one of his most famous tricks, The Light and Heavy Chest. Robert-Houdin brought a small wooden box on stage and declared that he had found a way to protect it from thieves. He would then ask a small child to lift it, which the child would do with ease. Then he would pick a full-grown man from the audience and ask him to lift the chest. And try as he might, the man could not lift the box. What was unknown to the audience is that the chest had an iron plate embedded in its based and under the stage was a powerful electromagnet which the magician could turn off and on by a hidden switch.What made this trick even more incredible is that Robert-Houdin used it to help squelch a rebellion in French Algeria. In 1856, after his retirement, Robert-Houdin was asked by Napoleon III to help pacify the Marabouts there. The Marabouts were able to control their tribe with their “magical” abilities and had advised their leaders to rebel against the French. Napoleon wanted Robert-Houdin to show that French magic was more powerful. Robert-Houdin used The Light and Heavy Chest trick by inviting the strongest tribesman on stage and asking him to pick up the wooden chest, which he did with ease. Then Robert-Houdin announced that he was going to take his strength. Waving his wand he declared, “Now you are weak.…Try to lift the box.” The tribesman laughed at this and struggled with all his might trying to lift the chest, but it would not move! Then he tried to rip it apart, but the box had been rigged to give an electric shock when he tried to rip the handles off. Screaming in pain, the tribesman let go of the chest and ran out of the theater.After his performances were done, he visited with the tribe leader and was given a scroll professing the tribes loyalty to France and praising his magical powers. Robert-Houdin went back to France with his mission accomplished, having suppressed any possible rebellion.

Monday, October 17, 2011

A demonstration of the Meisner effect: a superconductor in transition to its superconducting state in the presence of an applied magnetic field will cancel out nearly all magnetic fields within to achieve a locked levitation.

Saturday, October 15, 2011

Congratulations to Perlmutter, Schmidt and Riess for being award the 2011 Nobel Prize in Physics for the discovery of the accelerating expansion of the Universe. For nearly a century, we have known that the Universe is expanding as a result of the Big Bang about 14 billion years ago. However, their discovery in 1998 that this expansion is accelerating is astounding and has turned cosmology on its head.By studying more than 50 distant supernovas over time they discovered that not only is the universe expanding, but at an ever-accelerating rate. Supernovas are exploding stars similar in mass to the Sun but much denser. Supernovas can briefly outshine a whole galaxy. What they discovered was that their light was weaker than expected—a sign that the expansion of the Universe is accelerating. When we look at distant galaxies and supernovas we see that they are moving away from us, and more distant ones are moving away faster so really its not just an expansion away from us. Everything is moving away from everything else—space itself is getting bigger.

Estimated distribution of matter in the Universe.

One would expect the expansion of the universe is something that would slow down, due to the gravitational attraction of every object to every other object in the universe. But we are not completely baffled. Einstein, in his general theory of relativity, predicted that even empty space has energy—what we call dark energy. The acceleration is thought to be driven by dark energy, but just exactly what that is remains perhaps the greatest mystery in physics today. What is known is that dark energy makes up about 74% of the Universe. This dark energy pushes space itself and causes distant galaxies to move away from us faster and faster, and this is where the acceleration comes from. So cosmologists are attempting to understand what is going on. Is it really dark energy or some modification of that, or is it a modification of Einstein’s theory of gravity? Either way, it appears that the Universe will continue to expand, and galaxies will continue to move away from us. In 100 trillion years the last star will go dark and the Universe will become a very cold and lonely place. It reminds me of the science fiction short story "The Last Question" written by Isaac Asimov in 1956. In the story, the supercomputer known as AC was asked how the threat to human existence by an eventual heat death (lack of free energy) can be averted. Every time the question was posed, the computer responded "insufficient data", but in the last scene, the god-like descendants of humanity watch as the last stars flicker out as the Universe approaches its heat death. Humanity asks the computer one last time and even though it cannot answer, it continues to ponder the question even after all life ceases to exist. Eventually the computer comes up with an answer, but since there is nobody to report it to, it decides to show the answer by reversing entropy. The story ends with "And AC said: 'LET THERE BE LIGHT!' And there was light—"

Wednesday, October 5, 2011

Looking down at our planet from outer space, most of what you see is water. About 71% of Earth’s surface is covered by ocean, which is why Earth is sometimes called the Water Planet. But that name is a little deceiving when it comes to our ability to supply clean drinking water to the nearly seven billion people on the planet.

“Water of love, deep in the groundBut there ain’t no water here to be foundSomeday baby when the river runs freeIt’s gonna carry that water of love to me.”—Mark Knopfler, Dire Straits

Oceans account for 97.25% of our water. The other 2.75%—fresh water—is divided up between glaciers and polar ice (2.04%), ground water (0.68%), lakes and rivers (0.01%), and the rest in clouds, vapor and precipitation.

Visualizing Earth’s water supply as spheres.

Think of it another way. If you could gather up all the water on the planet into a sphere it would have a diameter of 1,380 km, or about 40% that of the Moon. Pretty massive, right? But how much of that is drinkable? First lets remove all the salt water. That leaves us with a sphere that is 458 km in diameter. But most of this water—almost three-fourths of it—is locked up in glaciers and polar ice. If we remove that, our sphere of drinking water shrinks considerably, down to 265 km in diameter. Yet most of this water is still not available to drink, being trapped underground. The sum total of all the drinkable fresh water, available in lakes, rivers, and other reservoirs, would make a sphere just 66 km in diameter. So even though we live on the Water Planet, its easy to see why we have a Water Problem. Take Lake Mead for example. Fed by the mighty Colorado River, it’s the largest reservoir in the United States. Since 2000, its water level has steadily declined from 370 m to a low of 330 m in November of 2010, only two meters above the critical level that would automatically trigger water rationing for much of the southwestern United States. And according to a 2008 study done by the Scripps Institution of Oceanography, there is a 50% chance that Lake Mead could run dry by 2021 if climate change and use projections hold true.